Bluegrass grew out of Old-Timey music (that's what the early old-time bands called it...e.g. Asa Martin, and earlier ones); Old-timey music grew out of the traditional ballads, love songs, fueding songs, play-party songs, etc. which made up the repertoires of the first settlers (on these shores) from England, Scotland, Ireland, Wales, mostly- with remnants of folks from several other countries who made it into the mountains of Southern Appalachia. That's the progression I see because I lived through it all.